Question: There were 28 people riding on a train before it stopped and some number of people got off. Now there is 1 person riding on the train. How many people got off the train at the stop?
Answer: The number of people who got off is the difference between the number who were riding before and the number who are riding now. The difference is $28 - 1$ people. $28 - 1 = 27$ people got off.